Method for producing a nonwoven material by hydrodynamic needling

ABSTRACT

The novel product consists of hydrodynamically bonded non-woven layers of which at least four layers are stacked and are than joined to one another by only using hard water jets.

From U.S. Pat. No. 6,110,848 there is known a three-ply sandwichnonwoven whose outer plies are made up of staple fibers 30-100 mm longand that has in the middle a pulp ply, which can also be made up of ablend of and with other fibers such as natural fibers or syntheticfibers.

It is an object of the invention to form a method for producing asandwich nonwoven that makes special properties possible. Thus, forexample, the end product is to have a high liquid absorption capacity onone side while the other surface is instead to be tight or better suitedto the absorption of other liquids, in any case is to differ in itsproperties from the other surface.

In order to achieve the object, provision is made for developing amethod for producing an at least four-ply sandwich nonwoven material bycontinuous forming of the plies, that is, first the base ply, then theat least two middle plies and finally the cover ply, then continuousbonding of the nonwoven material, four-ply in any case, by hydrodynamicneedling alone, followed by drying of the nonwoven material, the twoouter plies being produced from nonwovens of staple fibers up to 100 mmlong, which are produced by the carding method or formed from spun-bondor melt-blown fibers, and the at least two inner plies covered by theouter plies being produced from unlike pulp fibers or pulp fibersblended with synthetic fibers or natural fibers, and the middle plies,two in any case, having unlike liquid absorption capacities. The pulpfibers with other fibers such as synthetic fibers or natural fibers canalso be made up of absorptive substances such as for examplesuperabsorbers.

The possibility of producing the two inner plies from unlike fibers thathave unlike purposes and properties has the advantage that such a wipe,hygiene product or the like can perform unlike tasks on the twosurfaces. One side for example can absorb more liquid than the other,better rubbing or similar action being possible, however, with thisother surface. Thus one inner ply can be made up of longer pulp fibersup to 30 mm long while the other ply can be produced from shorter pulpfibers such as 2-5 mm or from hydrophilic synthetic fibers. Flax fibers,SAP fibers or those with a different cross-sectional profile can also beused. The two inner plies can both have absorptive properties butadditionally differ substantially.

The two outer plies are to be made up of carded fiber plies, fromspun-bond or melt-blown nonwovens or of fibers different in fiberstructure whose fiber lengths can be adapted to the product in question.It is also possible, however, to use a different nonwoven formingprocess such as spun-bond, melt-blown or the Nanoval method according toDE-PS 199 29 709. Naturally, individually completely preformed tissueplies can also be laid on for sandwich nonwoven formation. A sandwichnonwoven formation is also conceivable in which the individual plies arewithdrawn from a roll with rolled-up individual nonwovens, meshes, wovenfabrics and the like. If a carding machine is to be used, which producestwo or three carded fiber plies at once (i.e., via two or threedoffers), then of these only the top ply can be subjected tocalendering, hot-air bonding or another kind of pre-bonding, so that thebottom ply, which governs the feel of the finished product, remainsvelvety.

1. A method for producing an at least four-ply sandwich nonwovenmaterial comprising continuous forming of a nonwoven material comprisingfirst a base ply, then the at least two middle plies and finally a coverply, then continuous bonding of the nonwoven material by hydrodynamicneedling alone, followed by drying of the nonwoven material, the baseply and the cover ply being formed from nonwovens of staple fibers up to100 mm long, which are produced by a carding method, or of spun-bond ormelt-blown fibers and the at least two middle plies covered by the baseply and cover ply being produced from pulp fibers or pulp fibers blendedwith synthetic fibers or natural fibers, wherein one of the at least twomiddle plies is produced from fibers different than fibers from whichanother of the at least two middle plies is produced and has unlikeliquid absorption capacities than those of the another of the at easttwo middle plies.
 2. The method for producing a nonwoven material ofclaim 1, wherein one of the middle plies is produced from a mesh-likenonwoven, a mesh of arbitrary plastic or of arbitrary other fibers. 3.The method for producing a nonwoven material of claim 1, wherein thesandwich nonwoven is outwardly covered by a mesh-like layer.
 4. Themethod for producing a nonwoven material of claim 1, wherein one of themiddle plies is made of pulp fibers up to 30 mm long and another of themiddle plies is made of shorter pulp fibers shorter than the pulp fibersof the one of the middle plies or from hydrophilic synthetic fibers.